Numbuh One, also known as Nigel Uno, is the bald, British leader of the Kids Next Door. His own father was once the KND's greatest agent, Numbuh Zero, and now Numbuh One spends his time devising elaborate plans for world domination that are just too cool not to try.
Hoagie P. Gilligan Jr may have some nerdy hobbies (like collecting cards) and a massive appetite, but he's smart enough to be the creator of the KND's wacky flying vehicles and weapons - including Sector V's tree-house.
Kuki Sanban is a cute, happy-go-lucky girl who will do anything to help the KND's cause... just as long as she can remember what that thing is! She also has a great love for and extensive knowledge about Rainbow Monkeys.
Numbuh Four, real name Wallabee Beetles, is always the first to rush into things and the first to ruin them. He's also easily fooled - ending up with him volunteering by mistake for the most dangerous KND missions!
Abigail "Abby" Lincoln only speaks when there's something important to say, and always keeps her cool. She's one of the few Kids Next Door who has any common sense.